عرض بوربوينت درس CLASSIFICATION OF THE ELEMENTS في الكيمياء للصف العاشر

2-2: CLASSIFICATION OF THE ELEMENTS

OBJECTIVES:

TO CLASSIFY ELEMENTS IN THE PERIODIC TABLE INTO METALS, NON-METALS AND METALLOIDS.

TO CLASSIFY ELEMENTS INTO GROUPS.

Focus Question

Why do elements in the same group have similar properties?

Review Vocabulary

valence electron: electron in an atom’s outermost orbital; determines the chemical properties of an atom

Electron configuration determines the chemical properties of an element.

The number of valence electrons in an atom is related to its position on the periodic table.

All group 1 elements have one valence electron.

Electron Configuration of Group 1 Elements

Period 1، hydrogen، 1s1، Period 2، lithium، 1s2s1، [He]2s1، Period 3، sodium، 1s22s22p63s1، [Ne]3s1، Period 4

potassium، 1s22s22p63s23p64s1، [Ar]4s1

Group 2 elements have two valence electrons.

The number of valence electrons for elements in groups 13–18 is ten less than their group number.

Within the group, the number of valence electrons remains the same which shows that the chemical elements present in the same group have the same number of valence electrons.

Example: elements present in first group hydrogen, lithium, sodium have the same number of valence electrons that is 1.

The energy level of an element’s valence electrons indicates the period on the periodic table in which it is found.

Noble Gas Electron Configuration

Period، Principal Energy Level، Element، Electron Configuration، n = 1، helium، 1s2، n = 2، neon، [He]2s22p6، n = 3، argon

[Ne]3s23p6، n = 4، krypton، [Ar]4s23d104p6

The periodic table is divided into four blocks: s, p, d, and f.

The blocks correspond to which energy sublevel in the element is filled or partially filled with valence electrons.

s-block elements consist of groups 1 and 2, plus the element helium.

Group 1 elements have a partially filled s orbital with one electron.

Group 2 elements have a completely filled s orbital with two electrons.

The p-block consists of groups 13–18, which fill the p orbitals.

In group 18, both the s and p orbitals of the period’s principal energy level are completely filled.

The d-block contains the transition metals. It is the largest block.

There are exceptions, but d-block elements usually have filled outermost s orbitals and filled or partially filled d orbitals.

The five d orbitals can hold 10 electrons, so the d-block spans ten groups on the periodic table.

The f-block contains the inner transition metals.

f-block elements have filled or partially filled outermost s orbitals and filled or partially filled 4f and 5f orbitals.

The seven f orbitals hold 14 electrons, and the inner transition metals span 14 groups.

Electron Configuration and the Periodic Table

EVALUATE THE ANSWER

The relationships between electron configuration and position on the periodic table have been correctly applied.

Use with Example Problem 1.

Problem

Strontium, which is used to produce red fireworks, has an electron configuration of [Kr]5s2. Without using the periodic table, determine the group, period, and block of strontium.

Response، ANALYZE THE PROBLEM

You are given the electron configuration of strontium.

KNOWN، UNKNOWN

Electron configuration = [Kr]5s2

Group = ?

Period = ?

Block = ?

SOLVE FOR THE UNKNOWN

For representative elements, the number of valence electrons can indicate the group number.

The s2 indicates the strontium’s valence electrons fill the s sublevel. Thus, strontium is in group 2 of the s-block.

The number of the highest energy level indicates the period number.

The 5 in 5s2 indicates that strontium is in period 5.

Period 7، Group 7، Group 1

What consists of elements with one valence electron?

unrelated to their group number

ten less than their group number

ten more than their group number

equal to their group number

For elements in groups 13-18, the number of valence electrons is ______.

the f-block

the d-block، the p-block، the s-block

In which block is group 17 on the periodic table?